This invention generally relates to ink jet printers and methods therefor and more particularly relates to an ink jet printer and method capable of forming a plurality of registration marks on a receiver and sensing the marks formed thereby to precisely translate the receiver in a manner avoiding use of a precision motor.
Ink jet printing is a popular technique for printing color images. The advantages of nonimpact printing, low noise, low energy use, low cost of operation, avoidance of toner transfers and fixing, and the ability to print on plain paper receiver are largely responsible for wide acceptance of ink jet printing in the marketplace.
In this regard, an ink jet printer produces text and color images on a receiver by ejecting ink droplets of cyan, magenta, yellow and black onto the receiver in an image-wise fashion. The different lines of the image are each deposited in separate printing passes, so that each printing pass forms one or more individual lines of an image. Combination of the lines forms the complete color print after all lines have been printed. It is known that such ink jet print heads can take any one of several forms including piezoelectric ink jet, thermal ink jet, and so-called "BUBBLE JET".TM. ink jet.
Moreover, a typical ink jet printer includes a print head translatable in a first direction and a plurality of rollers for translating the receiver in a second direction orthogonal to the first direction. As the print head and receiver are translated, the color image is printed onto the receiver in a series of image bands, which typically overlap, each band corresponding to dots printed in a single scan of the printhead in the first direction. That is, as the print head is translated in the first direction, a predetermined amount of ink is ejected at selected locations in order to print an image band. At this point, the rollers are operated typically by means of a precision motor, such as a stepper motor, to translate the receiver in order to print another image band. In this manner, a color image is printed consisting of a plurality of rows of printed dots (image rows) along the first direction. After printing of the image, the receiver is then ejected from the printer to receive the next sheet of receiver for printing another image.
However, it is important that individual image bands be in alignment (i.e., in registration) with each other in order to provide an aesthetically pleasing print. Indeed, each image band is expected to be in registration to only a few micro meters with neighboring image bands. Registration is conventionally provided by the use of the precision motor which advances the receiver during the printing process in steps after each pass of the ink jet printhead.
In the color impact printing art, use of registration marks to align separate color planes of an image (cyan, magenta, yellow and black) is known. These registration markers indicate the start and end of the image in each color plane. Reference is made to these marks as separate color planes are printed, so that individual color planes are in registration. In this regard, a registration mark is a symbol or collection of marks, such as a bar code, which convey information to the printer about the receiver. Such registration marks may be produced using optical, magnetic, electrical, tactile or other method that is easily readable.
Use of registration marks to achieve registration of color planes is known. One such technique is disclosed in U.S. Pat. No. 5,434,956 titled "Method And Apparatus For Printing An Image In A Specified Positional Relationship With A Preprinted Registration Mark" issued Jul. 18, 1995 in the name of Myungsae Son, et al. In one embodiment of the Myungsae Son et al. device, an image is preprinted on a receiver in a known positional relationship with a two-dimensional registration mark. A new image is printed onto the same receiver as the preprinted image. These plural images, such as the several related images produced in a multicolor drawing, are aligned with each other according to the registration mark in order to achieve proper registration. However, this patent does not address the problem of controlling the movement of the printhead in relation to the receiver during the printing process, and only solves the problem of locating the registration mark that is used as a reference for aligning different portions or planes of an image.
As stated hereinabove, the receiver is typically translated with respect to the print head by a stepper motor to achieve accurate registration of the image rows. For example, an apparatus and method using a stepper motor for encoding positions of a web press is disclosed in U.S. Pat. No. 4,495,583 titled "Apparatus And Method For Encoding Positions Of Web Press Machines" issued Jan. 22, 1985 in the name of Dinesh G. Punater. This patent discloses an apparatus and method for encoding lateral setting within a web press that operates on a web. The apparatus may be any laterally adjustable machine for operating on the web, such as an imprinter, numbering unit, or a device for punching or perforating the web. The machine is mounted on a shaft for movement along the shaft. A stepper motor is connected to the shaft for rotating the shaft in order to provide pre-encodement alignment of the machine with respect to the web. However, stepper motors are costly and cumbersome, especially when the printer assembly is designed to be used as part of a compact portable device such as a digital camera. Therefore, another problem in the art is use of costly precision motors either for translation of the receiver or for movement of a machine that encodes a web press.
Therefore, there has been a long-felt need to provide an ink jet printer and method capable of forming a plurality of registration marks on a receiver and sensing the marks formed thereby to precisely translate the receiver in a manner avoiding use of a precision motor.